Causation in the Law

First published Thu Oct 3, 2019

In this context the basic questions concerning causation in the law
are: (i) what are the criteria in law for deciding whether one action
or event has caused another (generally harmful) event; (ii) whether
and to what extent causation in legal contexts differs from causation
outside the law, for example, in science and everyday life; and (iii)
what reason(s) (presumably based in the law’s use of causation
to attribute responsibility) explain and/or justify such differences
as may be found to exist.

1. Introduction

Seemingly the central interests that justify having an entry on
causation in the law in a philosophy encyclopedia are: to understand
just what is the law’s concept of causation, if it has one; to
see how that concept compares to the concept of causation is use in
science and in everyday life; and to examine what reason(s) there are
justifying or explaining whatever differences there may be between the
two concepts of causation. Other entries in this encyclopedia deal
with the nature of causation as that relation is referred to in
science and in everyday life. The philosophical interest in the
law’s concept of causation is largely comparative: how does the
law’s concept differ, if at all, from the more general concept
of causation analyzed in philosophy, and are there good reasons
explaining why there are such differences?

These three questions—what is the law’s concept of
causation and how and why does it differ from the general notion of
causation in science and everyday life—are deceptively simple in
their appearance. Yet describing a concept like causation as it is
used in a body of discourse such as law, depends on a number of
variables examination of which early-on will precisify the questions
later pursued in this entry. These preliminary, clarificatory
variables are four in number.

First: human law, unlike the “natural law” of morality, is
inherently parochial in the sense that human law varies from place to
place. (It does this because human law’s existence depends in
part upon facts of institutional history and these facts vary from
place to place.) So the question, “whose law?”, looms
large at the start of an enquiry such as this. What follows describes
causation as it is used in what may broadly be called the
Anglo-American legal tradition—the legal tradition of the United
Kingdom, the domains of its Commonwealth, and the United States.
Despite this confession of a somewhat parochial focus, there are
nonetheless universalist implications of this analysis. This is
because there are strong similarities in the legal uses of causation
in all presently existing legal systems, even when one is not confined
to those of the English-speaking world.

Second, even when we restrict our focus to the law of some one legal
tradition, within that tradition there will be discrete areas of law
that make use of causation in their liability rules, such as the areas
of contracts, torts, property, constitutional, and criminal law within
the Anglo-American legal tradition. It is arguable that the precise
contours (and maybe even the central notion) of causation differs
between such areas; for example, it is plausible to think that there
is a significant difference between contract law’s notion of
consequential damages following upon breach and criminal law’s
notion of the proximate causation needed to make out a completed crime
(Moore 2009a: Appendix). Accordingly, to prescind from any such
differences as may exist between areas of law, this entry focuses on
what those within the Anglo-American legal tradition regard as the
dominant usage of causation in the law, which usage is to assign
responsibility to actors who cause harms to others. The areas
of law where such assignment of cause-based responsibility
predominates is in the law of crimes and the law of torts. The entry
accordingly focuses on those two areas of law because they are central
to the Anglo-American (and probably to any) legal system’s use
of causation. They are also the areas of law in which (by far) the
greatest attention has been paid to causation in both law and legal
theory.

Third, we need to distinguish propositions of law containing
the concept of causation, from propositions about the law of
causation. Our concern is with the former kinds of propositions; the
latter propositions are the hypotheses of theorists (such as the
present writer) about the content of the propositions that obligate
legal professionals within their roles as legal professionals, i.e.,
law. But it is the law itself that is the data from which a
legal concept such as causation-in-the-law is to be extracted.

Fourth, teasing out the contours of a concept such as causation from a
body of discourse such as the law is not (just) a matter of quoting or
paraphrasing explicit legal definitions of that concept, no matter how
authoritative such definitions purport to be. Legal definitions of
causation are only the start of an analysis of what
“cause” means in law. Also needed are two other items. One
is the implicit concept of cause to be teased out from usages
of the concept in propositions of law. Complex legal concepts as used
in the decided cases will only rarely coincide completely with
official legal definitions (which Roscoe Pound [1910] called,
respectively, “the law in action” and “the law in
the books”), even when such definitions speak univocally in
favor of some particular concept.

The other additional item needed is the purpose or value served by
legal doctrines employing a concept of causation. Legal concepts are
functional (sometimes styled, “interpretive”) concepts in
that their meaning is shaped by the values they serve in the doctrines
in which they appear, as much as it is shaped by the linguistic
(definitional and usage) facts above mentioned (Fuller 1958).

The law’s concept of causation is thus a product of three
factors in combination:

Causation’s explicit definition in authoritative legal
texts.

Its implicit definition extracted from the totality of usages
of the concept in the legal doctrines making up a body of law.

The value(s) served by the use of a concept of causation in the
legal doctrines employing the concept.

In addition to these three factors (and remembering the cautionary,
third point made earlier distinguishing propositions of law from
propositions about law), there are theories about what
causation does or should mean in law. Such theories have been proposed
by legal theorists as they utter propositions about law. Such
theories, despite their non-authoritative source, have played a major
role in the history of thought about the nature of causation in the
law. Some of such theories, to the extent their content accurately
mirrors propositions of law, have even become part of the law of which
they are theories (Raz 2012).

2. The Law’s Explicit Definition of Causation

2.1 The dominant two-tier definition of causation in the law

The conventional wisdom about the causation requirement in both
criminal law and torts is that it in reality consists of two very
different requirements for liability. The first requirement is that of
“cause in fact”. Such conventional wisdom holds that the
“cause-in-fact” requirement is the only truly
causal component of the law’s two requirements (despite
the fact that both are framed in causal terms), because this doctrine
is the only one that corresponds with any scientific or even factual
notion of causation. Whether cigarette smoking causes cancer, whether
the presence of hydrogen or helium caused an explosion, are factual
questions to be resolved by the best science the courts can muster,
and these are classed as “cause-in-fact” questions. By
contrast, it is contested whether the second requirement, that of
“proximate” or “legal” cause, is an evaluative
issue, to be resolved by arguments of policy, or whether it too is a
matter of causal fact. Suppose a defendant knifes his victim, who then
dies because her religious convictions are such that she refuses
medical treatment while knowing that such refusal will kill her
(Regina v. Blaue). Has such a defendant (legally) caused her
death? The doctrines of proximate cause are used to resolve such
questions, it being controversial whether such resolutions are matters
of natural fact or of moral fact (“policy”).

2.2 The dominant definition of cause-in-fact

Those who accept the conventional division of causation in the law
into two parts, then posit a very minimalist notion of the first
requirement, that of “cause-in-fact”. This minimalist
requirement is by far the dominant explicit test for cause in fact in
both torts and criminal law. It is the “sine qua
non”, or “but-for” test. Such a test asks a
counterfactual question: “but for the defendant’s action,
would the victim have been harmed as she was?” This test is also sometimes
called the necessary condition test, because it requires the
defendant’s action have been necessary to the victim’s
harm. The appeal of this test stems from this fact. The test seems to
isolate something we seem to care a lot about, both in explaining
events and in assessing responsibility for them, namely, did the
defendant’s act make a differencevis-à-vis how the world would have been had she not
done what she did? Insofar as we increase moral blameworthiness and
legal punishment for actors who cause bad results (and not
just try to), we seemingly should care whether a particular bad result
would have happened anyway, even without the defendant.

2.3 The dominant definition(s) of proximate cause

There is no equivalently clear, crisp definition of legal or proximate
cause. At the general level of an overall definition, the most one
gets are the bromides: that a proximate cause cannot be
remote from its putative effect; it must be a direct
cause of the effect; it must not involve such
abnormality of causal route that is freakish; it
cannot be of harms that were unforeseeable to the actor; its
connection to the harm cannot be coincidental; it must make
the harm more probable; etc. These bromides are often uttered
as if they were synonyms, which in truth the decided cases reveal that
they are not.

3. The Data from Which an Implicit Concept of Legal Cause Is to Be Extracted: Fifteen Legal Facts About Cause-Based Liability in Anglo-American Tort and Criminal Law

To the definitions just mentioned, we should add the usage facts about
how “causation” is used in resolving the problems that
arise in particular cases. This allows one to compare the
explicit legal definitions of causation that we have just
surveyed with the concept of causation implicit in the
decided cases. It also allows philosophers to compare their favored
resolutions of various causal conundrums with the resolutions of those
same conundrums by people who have no philosophical axes to grind but
whose deliberations carry real world consequences with them, i.e.,
judges. (As J.L. Austin (1957) said, philosophers may have as much to
learn from lawyers on such issues as causation, as lawyers do from
philosophers.) With considerable selectivity, some simplification, and
little claim to completeness, fifteen facts are below selected as
salient in the legal usage of the concept of causation.

1. In cases of actions rather than omissions, usually (but not
always—see the discussion below of the action-overdetermination
cases) if the harm did not counterfactually depend on the
defendant’s action, then the defendant is not liable for that
harm because he is not said to have caused it (American Law Institute
1962).

2. If the defendant’s act does not increase the probability of
some harm occurring, and particularly if that act decreases such
probability, then the defendant is not liable for that harm because he
is not said to have caused it, even if that harm’s occurrence
counterfactually depended on the defendant’s action
(Oxendine v. State).

3. With regard to liability for omissions, usually there is no
liability for omitting to prevent some harm even in cases where there
is counterfactual dependence of the occurrence of that harm on that
omission; yet sometimes (the status, undertaking, and causing of peril
exceptions) there is such liability (so long as the occurrence of the
harm counterfactually depends on such omission; Dressler 1995:
466–467).

4. With regard to liability for “double preventions”
(where, for example, a defendant prevents a lifeguard from preventing
another from drowning), usually there is a supposedly cause-based
liability for the unprevented harm in such cases because a defendant
preventing a preventer from preventing some harm is regarded as the
cause of that harm. Yet sometimes (for double preventions amounting to
the “allowings” as conceived by the centuries-old
doing/allowing distinction) double preventions are treated just like
omissions so that there is no legal causation and no liability except
for those exceptional circumstances (the status, undertaking, and
causing of peril exceptions) that exist for omission liability (Moore
2009a: 61–65, 459–460).

5. In cases of probability-raising actions, omissions, and
doubly-preventative actions, there is occasionally and inconsistently
still no liability for harms that counterfactually depend on such
actions, omissions, and double preventions if such harm does not also
counterfactually depend on that aspect of those actions, etc., that
made the defendant culpable.

6. There is a complex pattern of liability for multiple cause cases
involving actions: First, in ordinary, garden-variety concurrent cause
cases (two or more factors individually necessary and only jointly
sufficient for some harm), there is commonly liability even though the
defendant’s act is but one of many causal factors producing a
harm and such liability is full (“joint and several”)
individual liability of such co-causing joint tort-feasors in torts
and co-causing principals in criminal law. Second, in the symmetrical
overdetermination variety of concurrent cause cases (where two or more
factors are individually sufficient and only jointly necessary for
some harm), there is universally liability where the acts of each of
two or more culpable defendants is independently sufficient (and thus
not individually necessary) for the harm, and there is almost always
liability where the sufficient condition alternative to the
defendant’s action is not the act of another human agent but is
a natural event or condition such as an avalanche. Third, there is
also liability in mixed cases (“mixed” between
overdetermination and garden variety concurrent cause cases in that
there are three or more factors, any two of which are sufficient for
the harm, meaning no factor is individually necessary for that harm;
Johnson 2016). Fourth, there is also liability in asymmetrical
overdetermination concurrent cause cases, these being cases where one
factor is sufficient and other factors are neither individually
necessary nor individually sufficient, such liability uniformly being
imposed for the big cause (the sufficient factor) and non-uniformly
and inconsistently being imposed for the little causes (the
insufficient and unnecessary factors; Wright 1985b). Fifth, in the
pre-emptive variety of multiple cause cases (where one sufficient
factor pre-empts another equally sufficient factor from operating on
this occasion), there is liability for the pre-empting sufficient
factor but there is no liability for the pre-empted sufficient
factor.

7. There is also a complex pattern of liability for a harm in multiple
cause cases involving omissions that is different than it is for
actions, even when we restrict our gaze to omission cases where there
is a legal duty on each omitter not to omit to prevent that harm:
First, there is liability on each omitter in ordinary, garden-variety,
concurrent omission cases just as there is in multiple cause cases
involving actions and not omissions. Second, predominantly (but not
universally) there is no liability for the overdetermination
variety of concurrent omissions—this is universally true where
one of the absences sufficient for the occurrence of the harm is
natural, not human, and it is predominantly true where all of the
absences individually sufficient for the occurrence of the harm are
the omissions of culpable human actors (Fisher 1992). Third, there are
no pre-emptive omission cases because such cases are conceptually
impossible, and thus any liability questions here are moot (Moore
2011b: 479–482; 2013: 342–348).

8. There is also a complex pattern of liability for a harm in multiple
cause cases involving double preventions rather than actions or
omissions, and this pattern of liability is different yet again than
it is in cases of actions or omissions: First there is liability in
ordinary, garden-variety, concurrent double-prevention cases just as
there is for actions and omissions. Second, there is predominantly
(but not universally) no liability for the overdetermination
variety of concurrent double-preventions—this is universally
true where one of the doubly-preventative acts sufficient for the
occurrence of the harm is a natural event, not a culpable human
action, and it is predominantly true where all doubly-preventative
acts sufficient for the occurrence of the harm are the actions of
culpable human actors (Moore 2009a: 466–467). Third, unlike in
omission cases, there is such a thing as a pre-emptive double
prevention case; in such cases, there is liability for the pre-empting
double prevention but not for the pre-empted action that would
otherwise have been a double prevention (Moore 2011b).

9. Liability exists for harms caused by a defendant even though such
harms would not have occurred but for the victim’s freakishly
abnormal condition so long as that condition pre-existed the
defendant’s action (this is the common law’s
“thin-skulled man” or “you take your victim as you
find him” maxim).

10. Yet no liability exists for harms in part caused by a defendant if
that harm was also in part caused by a freakishly large natural event
that intervened between the defendant’s act and the harm that he
in part caused (the “vis major” part of the
common law’s “superseding cause” doctrine; Larremore
1909).

11. There is no liability for harms due to a “coincidence”
(defined as a freakishly unusual conjunction of events) even though
such harms would not have occurred but for the defendant’s
culpable action, so long as that coincidence is not used by the
defendant as a means to bringing about the harm (another part of the
common law’s “superseding cause” doctrine; Hart
& Honoré 1959, 1985).

12. Intention has supposed aphrodisiac powers to extend legally
relevant causal influence to what otherwise would be legally remote
events (the “no harm is too remote if intended” maxim of
the common law; Terry 1914: 17).

13. Under the intervening human actor branch of the common law’s
superseding cause doctrine, there is no liability if a subsequent
human actor (rather than a natural event) intervenes to “break
the causal chain” otherwise existing (because of counterfactual
dependence) between the harm and the defendant’s earlier act,
where that intervening actor:

Acts subsequently to defendant’s act, and is thus not a
co-causer of the harm.

Does an act that is causally significant with respect to the
harm.

Acts independently of any motive to so act supplied by the
defendant.

Acts with great culpability in bringing about the harm (usually
intentionally or sometimes recklessly, but not merely negligently,
with respect to the harm).

Acts voluntarily in the narrow, technical sense of the law,
namely, the relevant bodily movements are not reflexive, done while
asleep, unconscious, in shock, under hypnosis, or otherwise not the
product of the defendant’s will.

Acts voluntarily in the sense that he is not coerced by threats,
by natural necessity, or by the compunctions of legal duty.

Is a responsible agent (not very young, insane, or very
drunk).

14. The set of doctrines presupposing scalarity of the causal relation
as that relation is used in law (moore 2009a: 65–76, 118–123):

The use of “strength of causal connection” as one
factor (along with degrees of fault) in apportioning liability in
multiple cause cases in torts, of particular importance in strict
liability cases where liability does not depend on fault (American Law
Institute 2010: sec. 6).

The seeming dependence on degree of causal contribution to
license use of the balance of evils defense in cases of aiding nature
or other persons to cause harm, and in the redirection of force cases.

The puzzling use of something like degree of causal contribution
to license the balance of evils defense in the acceleration cases
(cases where the defendant merely accelerates a harm that was about to
happen anyway.

The “petering out” of degrees of causal contribution
in cases of simple spatio-temporal remoteness.

15. The absence of liability in the freakish route cases even when a
harm counterfactually depends on the defendants act, including both
cases where the route is freakish vis-à-vis the
defendant’s plans or expectation, and cases where the route is
freakish to an outside observer.

4. The Value(s) Served by Causal Requirements in the Law of Torts and of Crimes

There are two reasons to care about the rationale for the law’s
use of causation in the liability doctrines of tort and criminal law.
The less relevant one here is the legal reformer’s motive, which
is to assess what the best test for causation is and to recommend that
such a test ought to be legislated for future legal use. The
second, and the more relevant motive here, is the lawyer’s
motive, which is to understand what the requirement for causation
presently is under existing law. As was previewed in
section 1,
what the law provides on a given topic like causation is in part
constituted by the function such a requirement serves in a body of
law, and such function thus constitutes the third ingredient we need
to consult as we reconstruct the law’s concept of causation.

Lawyers and legal theorists alike have an unfortunate penchant for
proclaiming that the law is, should be, and must be,
autonomous from other disciplines (such as philosophy) in its
use of concept like causation (Stapleton 2008; 2015). As Sir Frederick
Pollack put it over a century ago, “the lawyer cannot afford to
adventure himself with philosophers in the logical and metaphysical controversies that beset the idea of
cause” (1901: 36). Yet whether such conceptual autonomy is
desirable, necessary, or even possible, presupposes that the law has
purposes for its causal requirements that do not dovetail with the
metaphysics of causation so studied by philosophy.

As we will see below in
section 5.2,
the legal economists and other utilitarians believe that legal rules
attaching liability to those who cause harm, have as their
rationale preventing sub-optimal levels of such harms; they do this by
incentivizing future behavior by the placement of liability (or
rewards) on past behavior. On such a view, causation in the law might
well mean something different than it means when used in ordinary or
scientific discourse—for to gain incentive effects from
cause-based liability rules, one might well identify
“cause” with the raising of conditional probability, as
the legal economists have indeed often urged.

An alternative view of legal purposes, however, returns the law to the
metaphysics of causation. That view holds that criminal law serves the
value of retributive justice just as tort law serves the value of
corrective justice. Retributive justice requires that those who
culpably cause harm suffer the censure and deprivations constitutive
of punishment; corrective justice requires that those who culpably
cause harm to another correct that injustice by compensating that
other. In both cases, serving such kinds of justice demands that one
not identify “cause” as used in legal liability
rules as anything other than that with which it is identified in such
justice theories. Because such moral theories of justice require that
the true metaphysics of causation determines when someone has
caused an injury or other harm to another, so too must the
law of torts and of crimes. On such an alternative view of the
rationale for causal requirements in the law of torts and of crimes,
the lawyer thus must “adventure herself with the
philosopher” on the metaphysics of causation. Those who so
adventure themselves will not regard all the candidates for the
law’s concept of causation with equal favor.

What the law of causation needs to be if it is to serve the
value(s) constituting the function of the rules in which causation
appears, thus makes a considerable difference to what the law of
causation is. As we proceed to describe what the law’s
concept of causation is, we should be eclectic on what these values
are. We shall thus regard as unsettled what most theorists regard as
settled (not that they agree on how it is settled), and
consider things not only from the perspective of those who think that
criminal law and torts serve the ends of retributive and corrective
justice, but also from the perspectives of those who think that these
areas of law serve other values (both utilitarian and otherwise), or
even no coherent set of values at all.

5. Combining These Three Sources into a Concept of Causation in the Law

How one should combine these three ingredients—the explicit
legal definitions of causation, the concept implicit in legal usages
of “causation”, and the value(s) served by requiring that
causation be present before one be held responsible for some
harm—is a contested matter about which legal theorists have long
disagreed. The discussion that follows does not attempt to suppress
these disagreements. Different consolidations are thus described and
some problems are raised for each.

5.1 The variety of cause-in-fact tests in the law

The supposed dominance of the sine qua non test in the law is
superficial. The reality is that that test is modified/abandoned in a
variety of ways by the courts that are supposedly applying it. The
best way to understand the various modified tests for cause in fact in
law is by examining problems that have been raised for the
counterfactual test, for it is these problems that motivate
alternative tests of cause in fact.

5.1.1 Problems for the counterfactual test of cause-in-fact

Very generally, there are four sorts of problems with the
counterfactual test for causation in fact that are raised in the legal
literature. The first of these problems has to do with proof and
evidence. As an element of the prima facie case, causation in fact
must be proven by the party with the burden of proof. In criminal
cases, that is the prosecution, who must prove beyond a reasonable
doubt what would have happened absent the defendant’s act.
Counterfactuals by their nature are difficult to prove with any degree
of certainty, for they require the fact finder to speculate what would
have happened if the defendant had not done what she in actual fact
did. Suppose a defendant culpably destroys a life preserver on a
seagoing tug. When a crewman falls overboard and drowns, was a
necessary condition of his death the act of the defendant in
destroying the life preserver? (New York Central RR. v.
Grimstad). If the life preserver had been there, would anyone
have thought to use it? thrown it in time? thrown it far enough?
gotten it near enough to the victim that he would have reached it? We
often lack the kind of precise information that could verify whether
the culpable act of the defendant made any difference in this way.

A second set of problems stems from an indeterminacy of meaning in the
test, not from difficulties of factual verification. There is a great
vagueness in counterfactual judgments. The vagueness lies in
specifying the possible world in which we are to test the
counterfactual (Cole 1964a,b; Lewis 1973b). Suppose a
defendant negligently destroyed a life preserver and a sailor drowns
for want of one. When we say “But for the defendant’s act
of destroying the life preserver”, what world are we imagining?
We know we are to eliminate the defendant’s act, but what are we
to replace it with? A life preserver that was, alternatively,
destroyed by the heavy seas? A defendant who didn’t destroy the
life preserver because she had already pushed the victim overboard
when no one else was around to throw the life preserver to the victim?
And so on and so on. To make the counterfactual test determinate
enough to yield one answer rather than another, we have to assume that
those applying this test share an ability to specify some definite
possible world that is “similar” to our actual world save
that in that world the defendant did not do what she did in the actual
world.

The third and fourth sets of problems stem from the inability of the
counterfactual test to match what for most of us (including judges)
are firm causal intuitions. The third set of problems arises because
the counterfactual test seems too lenient in what it counts as a
cause. The criticism is that the test is thus overinclusive. The
fourth set of problems arises because the counterfactual test seems
too stringent in what it counts as a cause. The criticism here is that
the test is underinclusive.

The overinclusiveness of the test has mostly been raised in cases of
coincidence. Suppose a defendant culpably delays his train at
t1; much, much later at t2, and
much further down the track, the train is hit by a flood (Denny v.
New York Central RR). Had the delay at t1 not
occurred, there would have been no damage or loss of life at
t2. In this case, the counterfactual test yields the
unwelcome result that the defendant’s delaying caused the harm.
Such cases of overt coincidences are rare, but they are the tip of the
iceberg here, in that innumerable remote conditions are necessary to
the production of any event. Oxygen in the air over England, timber in
Scotland, Henry VIII’s obesity, and Sir Francis Drake’s
perspicuity, were all probably necessary for England’s defeat of
the Spanish Armada; but we should be loath to say that each of these
was a cause of that defeat. The problem is greatly exacerbated by the
admission of omissions as causes: the Spanish Armada was also defeated
because Martian spaceships didn’t show up to help them.

The fourth set of problems for the counterfactual test has to do with
the test’s underinclusiveness, mostly exhibited in legal theory
in the well-known overdetermination cases. These are cases in which
each of a pair of two events, c1 and
c2, is independently sufficient for some third event
e. Logically, the sufficiency of c1 and of
c2 entails that neither c1 nor
c2 is individually necessary for e, and thus,
on the counterfactual analysis of causation, neither of them can be
the cause of e. The law uniformly rejects this conclusion
(howevermuch some philosophers such as David Lewis have claimed
uncertainty in their own intuitions about there being causation in
such cases), so such cases pose a real problem for the counterfactual
analysis of causation in law.

Legal theorists have long distinguished two distinct kinds of
overdetermination cases. The first are the concurrent cause cases: two
fires, two shotgun blasts, two noisy motorcycles are each sufficient
to burn, kill, or scare some victim. The defendant is responsible for
only one fire, shot, or motorcycle. Yet his fire, shot, or noise joins
the other one, and both simultaneously cause their various harms. On
the counterfactual analysis, the defendant’s fire, shot, or
noise was not the cause of any harm because it was not necessary to
the production of the harms—after all, the other fire, shot, or
noise was by itself sufficient. Yet the same can be said
about the second fire, shot, or noise. So on the but-for test, neither
was the cause! And this conclusion has seemed absurd to legal
decision-makers.

The preemptive kind of overdetermination cases are different. Here the
two putative causes are not simultaneous but are temporally ordered.
The defendant’s fire arrives first and burns down the
victim’s building; the second fire arrives shortly thereafter
and would have been sufficient to burn down the building, only there
was no building to burn down. Here our intuitions are just as clear as
in the concurrent overdetermination cases, but those intuitions are
here different: the defendant’s fire did cause the harm, and the
second fire did not. Yet the counterfactual analysis again yields the
counterintuitive implication that neither fire caused the harm because
neither fire was necessary (each being sufficient) for the harm.

Situated rather nicely between these two sorts of overdetermination
cases are what have been called the asymmetrical overdetermination
cases (Moore 2009a: 417–18). Suppose one defendant non-mortally
stabs the victim at the same time that another defendant mortally
stabs the same victim; the victim dies of loss of blood, most of the
blood gushing out of the mortal wound. Has the non-mortally wounding
defendant caused the death of the victim? Not according to the
counterfactual analysis: given the sufficiency of the mortal would,
the nonmortal wound was not necessary for, and thus not a cause of,
death. This conclusion is contrary to common intuition as well as
considerable (but not universal) legal authority (People v.
Lewis).

5.1.2 Modifications/abandonments of the counterfactual test

Defenders of the counterfactual analysis of
“cause-in-fact” are not bereft of replies to these four
objections, but rather than pursuing this further we shall move on to
discuss other tests that have been substituted for the counterfactual
test in an attempt to avoid these four problems. With regard to the
problem posed by the overdetermination cases, the best known
alternative is to propose an “INUS” (an Insufficient but
Necessary element of an Unnecessary but Sufficient set) test (Mackie
1980) or a “NESS” (Necessary Element of a Sufficient Set)
test (Wright 1985b; 2013): an event c causes an event e
if and only if c is a necessary element in a set of conditions
sufficient for e where the set itself need not be necessary for
e. It is the stress on sufficiency in these tests that
is supposed to end-run the overdetermination problems. In the
concurrent cause cases—the two sufficient fires joining to burn
the victim’s house—each fire is said to be a necessary
element of its own sufficient set, so each fire is a cause. In the
preemptive case—the fires do not join and one arrives first
before the second can get there to do the job—the first fire is
a necessary element of a sufficient set, and so is the cause; the
second fire is not, because it is not thought to be part of a set that
is sufficient at the time of the destruction (absent from its set is
the existence of a house to be burned).

Other modifications of the counterfactual test have also been adopted
in order to avoid problems for the test existing because of the
overdetermination cases. One of these is the “fine-grained
effect” approach of the Commentary to the Model Penal Code. On
this test, one does not ask whether a harm of a certain type
would have occurred but for the defendant’s act; rather, one
asks whether the particular harm that actually occurred would
have occurred in the exact way that it did, in the absence of the
defendant’s act. So in the concurrent cause case of the two
independently sufficient fires that join to burn down the
victim’s house, we do not ask,

Was the defendant’s fire necessary to a destruction of
plaintiff’s house?

Rather, we ask,

Was the defendant’s act necessary to the destruction of
the victim’s house where, when, and in the manner that it was
destroyed?

It is much more likely that the defendant’s fire was
necessary to the destruction of the victim’s house in just the
way it was destroyed, so the counterfactual test seems to do better in
the concurrent overdetermination cases with this fine-graining of the
effect approach.

For the preemptive overdetermination cases, the problem is easier for
the counterfactual test. Here one introduces a stipulation about the
time of the event: if the defendant’s act was necessary to the
house destruction being earlier than it otherwise would have been,
then he was the cause, but if his act was only necessary to the house
destruction happening at some time or other (including later), his act
is not necessarily the cause. As the cases put this point, causes must
accelerate their effects; if they fail to accelerate them
(either by making no change in temporal location or by retarding
them), then such factors are not causes even though necessary to when
the putative effect happened (Oxendine v. State). This helps
with the preemptive cause cases because a preempting fire is necessary
to a house’s destruction at t1, even if (given that
there is a preempted fire right behind it at t2)
that first fire is not necessary either to a house destruction later
(at t2) or to a house destruction sometime
(t1 or t2). This stipulation
regarding temporally asymmetrical necessity should be regarded as a
third modification of the law’s counterfactual test.

The coincidence objection to the counterfactual test yields a fourth
modification to that test. In cases like that of the negligently
speeding train that, because of its speed, arrives at just the place
where a falling tree hits it (Berry v. Borough of Sugar
Notch), one should not ask, “But for the act of driving
would the train have been hit?” Rather, one should isolate
that aspect of the act that made it negligent—speeding,
not the act itself—and ask whether that aspect was necessary to the
train having been struck. And arguably driving in excess of the speed
limit (“speeding”) was not necessary for the impact because any speed
above as well as below the speed limit would have resulted in no
impact on the train. Speeding, in other words, wasn't necessary, only
the exact speed at which the driver in fact drove. Asking after the
necessity of qualities of acts like speeding is called the
“aspect cause” version of the counterfactual test (Keeton
1963; Wright 1985b).

A fifth modification to the counterfactual test of cause in fact is
more by way of substitution than of amendment. This is the First and
Second Restatement of Torts “substantial factor”
test. Motivated mostly by worries about overdetermination cases, the
American Law Institute in both of its first two Restatements
urged that a “substantial factor” test be substituted for
sine qua non as the test for cause-in-fact in torts. The test
asks only whether a defendant’s action was a substantial factor
in the production of the harm complained of. This admittedly circular
and vague test was thought to help in overdetermination cases like
that of the joint fires, because so long as each fire was quite
substantial (in comparison to the other fire) each was a cause of the
harm, even though neither fire was a necessary condition of the
harm.

Notice that the substantial factor test “solves” the
overdetermination problem mostly because it does not say enough to get
itself into trouble in such cases. It thus allows our clear causal
intuitions full play in these cases. The ad hoc nature of
this solution is evident when one sees how the First and Second
Restatement of Torts managed to salvage what they could of
the sine qua non test: if a putative causal factor is a
necessary condition of some harm, then (under the
Restatements) it is per se substantial. Necessary
condition–hood, in other words, is sufficient for cause
in fact. But necessary condition–hood is not necessary
for cause in fact, so that a factor can be substantial even if it is
not a necessary condition. This amounts to saying that one should use
the necessary condition test when it works, but when it yields
counterintuitive results (as in the overdetermination cases) one
shouldn’t use it but should rely instead on causal intuitions
that are not based on counterfactual relations. As much is admitted in
a recent revival of the two Restatements’ primitivism
about causation, according to which one is explicitly directed to find
either counterfactual dependence of a harm or “actual
contribution” to that harm (Stapleton 2015).

The sixth and final modification of the counterfactual test of cause
in fact is motivated by the proof problem. Particularly in criminal
cases (where one has to prove causation “beyond a reasonable
doubt”) it is often impossible to prove that the harm would not
have happened but for the defendant’s act. What courts in effect
adopt is a “lost chance” approach to counterfactuals. On
this modified test, one does not ask whether the act was necessary to
the harm actually occurring; rather, one asks only whether the act was
necessary to the harm having the chance of occurring that it did
(Lewis 1986). This is a “necessary to chance (of harm)”
sort of test, not a “necessary to harm” test (Johnson 2005).

What courts and legal theorists have actually done in
“modifying” the counterfactual test in these six ways is
to propose quite different theories about the nature of causation. The
INUS and NESS tests, for example, are in reality nomic sufficiency
tests, a version of a generalist theory of
causation that reduces singular causal relations to general causal
laws and does not make essential use of counterfactuals (except
insofar as counterfactuals are part of the analysis of the idea of a
scientific law.) The substantial factor test, to take another example,
is really the law’s version of a primitivist approach to
singular causation, a version of singularist theories of causation in
metaphysics. The necessary-to-chance modification is in
reality the substitution of a probabilistic theory of causation for a
purely counterfactual theory. It is thus a mistake to think that the
law’s explicit definition of cause in fact—sine qua
non—in fact evidences any deep or univocal commitment of
the law to a theory of causation that is truly counterfactual in its
nature (as is for example Lewis 1973a).

5.2 Skeptical approaches to the cause-in-fact requirement

Legal theory, like philosophy, has had its share of skeptics about
causation. Most of such legally located skepticism has been directed
at the proximate cause half of the conventional two-part definition of
causation in the law. As we shall see shortly, such skepticism there
considers “proximate cause” a misnomer and
reinterprets the proximate cause requirement in noncausal, policy
terms. More radical is the skepticism here considered. Some legal
theorists are skeptical of there being any natural relation in the
world named by “causation”. This skepticism includes what
the law names “cause in fact” as well as “proximate
cause”.

Before we describe such skepticisms in legal theory, we do well to be
sure we have a firm grasp on what skepticism about causation is. Take
David Hume, often listed as a skeptic about causation. Hume famously
identified singular causal relations as spatiotemporally located
instances of causal laws, and he identified causal laws as no more
than uniformity in sequence between types of events. Hume was thus
doubly a reductionist about the causal relation, reducing it
ultimately to regular concurrence. In this, he is commonly said to be
a skeptic.

Because Hume’s analysis takes “the glue” out of the
causal relation—a cause doesn’t make its effect
occur, it is only regularly followed by its effect—it is
commonly classified as skeptical. And in a sense it is, if one treats
the making-things-happen “glue” to be essential to any
relation properly called “causal”. But Hume’s views
are not radical enough to count as skeptical in the sense intended by
legal theoreticians. For Hume gives what Saul Kripke calls a
“skeptical solution” to the problem of causation (1982:
66–68): Hume doesn’t deny that causation exists, but he
reduces it to something less ontologically queer than
“glue”.

A better model of the radical skepticism here considered is the
“ascriptivist” views that Herbert Hart once held (but
later repudiated). In a famous analysis of our usage of the causative
verbs of action such as “A hit B”, Hart
urged that we describe no natural relations (such as that
A caused there to be contact on B’s body), but
rather we ascribe responsibility to A for the contact
on B’s body. (Hart 1949) If this bit of pre-Austin speech act
analysis were true, then causatives (and analogously, more explicit
words of causation) would only be the labels used to express
conclusions about responsibility. Such words would not name real
relations that could be the justifying grounds for attributing
responsibility to someone.

Such are the conclusions of the legal skeptics here considered. Such
skeptics appear to deny that causation exists as any kind of natural
relation, be it a “glue-like” natural relation, regular
concurrence in nature, or something else. Because it is easiest to
approach such skepticism historically, I shall begin with the badly
named American Legal Realists (badly named because in no sense were
they realists in the philosophical sense), with whom almost all of the
skepticisms about proximate causation also originated.

5.2.1 The skepticism about causation of the American Legal Realists

Most of Henry Edgerton’s much-cited work details his skepticism
about proximate causation. Some of it, however, reveals him to have
been a skeptic about the cause-in-fact requirement as well. He notes,
for example, that the symmetrically concurrent overdetermination cases
were divided into two camps by the cause-in-fact doctrines of his day:
where there were two culpable actors starting fires (where
the fires joined to produce a larger fire burning down the
plaintiff’s house), either actor was a cause of the destruction;
but when only one of the fires was of culpable origin, the other being
either natural or of innocent human origin, then the culpable
actor was not a cause of the destruction. From such examples, Edgerton
suggested that the cause-in-fact requirement was (like the proximate
cause requirement) all a matter of policy, a matter, that is,
depending on “our free and independent sense of justice
and—perhaps—the interests of society”.

A late blooming of this Legal Realist conclusion was the well-known
work of Wex Malone (1956). Malone largely focused on an issue that
preoccupied philosophers of causation in the 1950s: the pragmatic
features by which we pick out “the cause” of some
event (Feinberg 1970: 143–147). Malone found, unsurprisingly, only
context-specific, practical interests guiding such locutions of causal
emphasis, and skeptically concluded that that was all there was to
causation itself. To be said to be “the cause” of some
harm was just another way of saying one was responsible for the
harm.

5.2.2 The skepticism about causation of the Critical Legal Theorists

The skepticism of American Legal Realism has had two intellectual
descendants in legal theory. One of these consists of the self-styled
“critical” theorists—the Critical Legal Studies
movement (or “Crits”) whose heyday was in the 1970s and
1980s in America. Much of this movement’s skepticism is simply
warmed-over postmodernism, itself a passing fashion in many
disciplines besides law (Moore 1989). More interesting intellectually
were criticisms that were not based on postmodernist platitudes but
were specific to causation.

Mark Kelman’s skepticism was of this latter kind. Kelman urged
that all causal requirements in the law were part of the
“liberal myth” of objective criteria for liability, but
rather than reciting (yet again) the platitude of the historically
situated knower, Kelman actually directed arguments against the
law’s cause-in-fact tests, arguments denying that such tests
mirrored anything in natural fact. Kelman accurately perceived that
the NESS variation of the counterfactual theory was an ineffectual
version of it, and he produced some of the criticisms of that
variation that others who are not causal skeptics have also pursued.
From the perceived failure of this one variation of the counterfactual
theory of cause in fact, Kelman concluded that cause in fact itself
cannot be a matter of fact (Kelman 1987).

The general, positive prescription that is supposed to flow from the
skepticisms of the Legal Realists and the Crits is not so clear. One
gathers that once skepticism (about causation being a matter of
objective fact) has removed the blinders, we can see that it is only
interests and policies that lead us to conclusions about moral
responsibility and legal liability. Presumably, then, the positive
prescription is for us to do this openly, balancing all relevant
considerations of policy in deciding who should be liable and then
casting those liability conclusions in terms of what was the cause of
what.

5.2.3 The skepticism about causation of the legal economists

The other intellectual descendant of the American Legal Realists on
causation is the law and economics movement in contemporary legal
theory. These theorists are seeking to show that legal rules and
institutions either are or should be efficient, in the
post-Pareto sense of that word distinctive of modern welfare
economics.

Like the Crits, legal economists tend to be radical skeptics about
causation. The leading early papers on causation all express
skepticism about “causation” picking out any real relation
in the world. On this skeptical view, lawyers are just doing intuitive
economics or some other policy balancing in their use of causal
idioms, because that is all they can be doing. Shavell
(1980), and Landes and Posner (1983) explicitly rely on Edgerton,
picking up precisely where Edgerton began his skepticism, in the
liability rules for symmetrically concurrent overdetermination
cases.

Like other skeptics about causation, the legal economists do not rest
content in their demythologizing of the metaphysics of causation. Such
economists also have a more positive account of what should be made of
the law’s causation-drenched requirements for liability. The
positive, reconstructive prescriptions of the law and economics
theorists differ from those of the Crits and the Legal Realists in
that the policy favored is much more specific: liability (including
the supposedly causal requirements for liability) should give
incentives for efficient behavior. Yet unnoticed by the economists was
that this monistic policy focus on efficiency made their causal
skepticism unnecessary and beside the point in their recommendations
about what “cause” should mean in law.

This is because if efficiency is the normative polestar for both tort
and criminal law, then there is a basis for denying the relevance of
the metaphysics of causation to the interpretation of legal usages of
“cause” that does not depend on any skepticism about that
metaphysics. Such a basis begins with the quite correct insight that
legal texts are to be interpreted in light of the purposes (values,
functions, “spirit, “mischief”, etc.) such texts
serve. Often such purposes will justify an interpreter in holding the
legal meaning of a term to be quite different from its ordinary
meaning in non-legal English. Whether this is so in the case of the
legal uses of “cause” depends on what one takes to be the
purpose of those legal texts that use “cause”. Consider
American tort law.. Following the welfare economics of A. C. Pigou
(1920), it was for a time fashionable to think that the purpose of
liability rules in tort law was to force each enterprise or activity
within an economy to pay its “true costs”. Those costs
included damage caused to others by the activity as much as they
included traditional cost items of production like labor, raw
materials, and capital. The thought was that only if each enterprise
paid its true costs would the goods or services produced by that
enterprise be correctly priced, and only if such correct pricing
occurred would markets achieve an efficient allocation of resources.
This came to be known as “enterprise liability” in the
tort law theory of 1950s America (Calabresi 1961).

If the point of tort law were to achieve an efficient allocation of
resources, and if such efficiency could be achieved only by
discovering the “true costs” of each activity when such
costs are defined in terms of that activity’s harmful effects,
then “cause” as used in tort liability rules should mean
whatever the metaphysics of causation tells us the word means. For on
this theory it is the harmful effects that an activity really causes
that are the true costs for that activity; and this rationale thus
demands a robust use of some metaphysical view about causation.

This Pigouvian view of tort law has given way to the post-1960 view of
Ronald Coase: tort law indeed exists in order to achieve an efficient
allocation of resources, yet such efficiency will be achieved whether
tort liability tracks causal responsibility or not. Coase’s
essential insight was that to economically rational actors opportunity
costs are real costs too, so that a forgone opportunity to accept a
payment in lieu of causing another person some harm already forces the
harm-causer to “internalize” all costs of his activities.
Such a harm-causer need not be liable for such harms in order to have
him pay for the “true costs” of his activity; he already
“pays” by forgoing the opportunity to be bought off by the
sufferer of the harm. As each harm-causer and harm-sufferer decides on
the desired level of his activity, he will thus take into account all
effects of his interaction without a cause-based tort liability
forcing him to do so (Coase 1960).

On this Coasean analysis of tort law, there is simply no need for
liability to turn on causation. Rather, either tort liability is
irrelevant to efficient resource allocation (in a world of low
transaction costs), or tort liability should be placed on the cheapest
cost-avoider (in a world where transaction costs are high) in order to
induce that person to take the cost-effective precautions. In either
case, legal liability should not track causal responsibility, for even
when there are high transaction costs the causer of a harm need not be
the cheapest cost-avoider for that kind of harm.

The irrelevance of causation to the giving of efficient incentives has
left economists struggling to make sense of the cause-in-fact
requirement of criminal law and tort liability rules. Since no
metaphysical reading of “cause” is appropriate to the goal
of efficiency, some policy calculus is given as the legal meaning of
“cause”. Such policy calculus typically generates a
probabilistic interpretation of “cause”, so that any
activity that raises the conditional probability of some harm that has
occurred is said to have “caused” that harm (Calabresi
1975). For any theory seeking to use the law to give incentives to
efficient behavior in a world of high transaction costs, this
probabilistic interpretation is seemingly just what is required. To
criticize such probabilistic interpretation of legal cause on the
ground that probability is a poor metaphysical account of what
causation is (Wright 1985a, 1987), would thus be beside the
point—so long as one adheres to the economists’
utilitarian views about the proper function of the concept of
causation in the law.

5.3 The variety of proximate cause tests in the law

It was useful in taxonomizing the seven variations of the
counterfactual test to show how such variations were produced in
response to problems perceived to exist for the first variation, which
was the simple, unmodified counterfactual test. While there is no test
of proximate causation that is comparably dominant in law (even if
only in lip service) to the counterfactual test of cause-in-fact, it
is nonetheless useful to display the various proximate cause tests as
they react to problems in other tests of proximate causation. Some
discussion of standard problems with each version of the tests within
legal theory is thus included as we describe what motivates others of
the tests.

The basic taxonomizing principle here is to separate tests that do not
view proximate causation as having anything to do with real causal
relations (the conventional view within legal theory) from tests that
are motivated by the contrary thought. We shall begin with the former
kind of test, what should be called policy-based proximate cause
tests. Policy-based proximate cause tests are themselves usefully
divided into two camps. Some—general policy tests—are
justified by their service of a wide range of policies, indeed, as
wide as are the policies that justify liability at all in torts or
criminal law. By contrast, other tests are in the service of only one
policy: the measurement of the culpability of the actor in terms of
the mental state she had or should have had as she acted.

Beginning with the general policy-based proximate cause tests: the
first of these are what we may call “ad hoc policy
tests”. The idea is that courts balance a range of policies in
each case that they adjudicate where a defendant has been found to
have caused-in-fact a legally prohibited harm. They may balance
certain “social interests”, like the need for deterrence,
with certain “individual interests”, like the unfairness
of surprising a defendant with liability (Edgerton 1924). Courts then
decide wherever such balance leads. Whatever decision is reached on
such case-by-case policy balancing is then cast in terms of
“proximate” or “legal” cause. Such labels are
simply the conclusions of policy balances; the labels have nothing to
do with causation in any ordinary or scientific sense (Green
1929).

The second sort of test here is one that adopts general rules of legal
causation. Such rules are adopted for various policy reasons also
having nothing to do with causation, but such rules differ from the
ad hoc test by their eschewal of case-by-case balancing;
rather, it is the per se rules of legal causation that are
adopted for policy reasons. Thus, at common-law the rule for homicide
was that death must occur within a year and a day of the
defendant’s harmful action, else he could not be said to have
legally caused the death. Analogously, the last wrongdoer rule of both
torts and criminal law held that when a single victim is mortally
wounded by two or more assailants, acting seriatim over time and not
in concert, only the last wrongdoer could be said to be the legal
cause of the death. As a third example, tort law for a time observed
what was called a “first house rule”, according to which a
railroad whose negligently emitted sparks burned an entire town was
only liable for the house or houses directly ignited by its sparks,
not for other houses ignited by the burning of those first burnt
houses (Ryan v. New York Central RR). There is no pretense of
making truly causal discriminations by such rules; rather, such rules
were adopted for explicit reasons of legal policy. The first house
rule, for example, was said to be justified by the policy of
subsidizing the then developing railroad industry by protecting it
from a liability that was thought to be potentially ruinous in its
extent.

The main problem with both ad hoc and rule-based policy tests
does not lie with their “functionalist” approach (Cohen
1935; 1937). to legal concepts such as causation, for we should always
ask after the purpose of the rule or institution in which a concept
figures in order to ascertain its legal meaning. Yet for anyone who
thinks that criminal law and torts have dominant, justice-oriented
purposes, the open-endedness of these policy tests will be
disqualifying. If retributive justice is the value served by criminal
law, and if such justice requires that we grade punishment
proportionately to causation, then criminal law’s proximate
cause tests should aid in finding when offenders really cause a harm.
Analogously, a tort law that uses causation to mark out those owing
duties of corrective justice will limit those owing such duties of
compensation to those who have really caused the harms for which
compensation is sought. On such a view of tort law, proximate
causation should aid in separating those who really have caused a harm
from those who have not. To serve both retributive and corrective
justice, thus, the last thing one wants to do is to define legal
causation so that the label names a balance of values rather than the
factual state of affairs (real causation) that determines moral
blameworthiness. The Legal Realists’ explicit policy tests are
anathema to any justice-oriented scheme of punishment or of
compensation.

This problem does not so obviously infect the next two policy-based
proximate cause tests, the foreseeability and the harm-within-the-risk
tests. For those tests do seek to describe a factual state of affairs
that plausibly determines both moral blameworthiness and connects a
defendant’s culpability to particular harms. These tests are
thus serving the kinds of policies that must be served by the concept
of causation in justice-oriented theories of criminal law and of
torts. Their novelty lies in their relocation of how and where legal
causation determines fault. On these theories, “legal
cause” is not a refinement of an admitted desert-determiner,
true causation; it is rather a refinement of another admitted
desert-determiner, culpable state of mind.

Consider first the well-known foreseeability test. Unlike the case
with the rule-based policy tests, here there is no multiplicity of
rules for specific situations (like long drawn out processes of death,
intervening wrongdoers, railroad fires, etc.). Rather, there is one
rule universally applicable to all criminal and tort cases: was it
foreseeable to a defendant at the time that she acted that her act
would cause the harm that it in fact caused? (Green 1967). This
purportedly universal test for legal causation is usually justified by
one of two policies: either the unfairness of punishing (or extracting
compensation from) someone for harms that they could not foresee, or
the inability to gain any deterrence by sanctioning such actors (since
the threat value of tort or criminal law sanctions is commonly thought
to be nonexistent for unforeseeable violations of liability
rules).

Some jurisdictions restrict the foreseeability test to one kind of
situation. When some human action or natural event intervenes between
the defendant’s action and the harm, the restricted test asks
not whether the ultimate harm to the victim was foreseeable but
rather, whether that intervening action or event was foreseeable to
the defendant when he acted. This restricted foreseeability test is
like the restricted rules we saw before and is unlike the universal
test of legal causation the foreseeability test usually purports to
be.

Precisely because it is a culpability test, the foreseeability test
becomes subject to its own policy-based objection. The objection is
that of redundancy. Why should we ask two culpability
questions in determining blameworthiness? After we have satisfied
ourselves that a defendant is culpable—either because she
intended or foresaw some harm, or because she was unreasonable in not
foreseeing some harm, the foreseeability test bids us to ask
“Was the harm foreseeable?” This is redundant, because any
harm intended or foreseen is foreseeable, and any harm foreseeable
enough to render an actor unreasonable for not foreseeing it, is also
foreseeable.

The only way the foreseeability test avoids redundancy is by moving
toward the other alternative here, the harm-within-the-risk test. That
is, the law could have said that in situations where the defendant was
culpable in intending, foreseeing, or unreasonably risking some harm
type H, but what his act in fact caused was an instance of harm
type J, one should ask whether J was foreseeable, a
different question than the one asked and answered as a matter of
mens rea (which was about H). Of course, H must
be “close” to J for there to be a mind guilty with
respect to the harm for which responsibility is sought. Yet this is to
do the work of the harm-within-the-risk test, which is to solve what
should be called the “fit problem” of mens rea
(fitting the harm actually done, J, to the harm foreseen,
intended, or risked, H; Moore 2011a). Moreover, it is to do such work badly.
Foreseeability is not the right question to ask in order to fit the
harm in fact caused by a defendant to the type of harm with respect to
which she was culpable (either because she intended to achieve, or
foresaw that she would cause, or unreasonably risked achieving, such a
harm). If to avoid redundancy the foreseeability test is to be
restricted to this non-redundant work, it is better abandoned for the
harm-within-the-risk test.

Let us examine, then, this fourth policy-based proximate cause test,
the misleadingly labeled “harm-within-the-risk” test. Like
the foreseeability test, this test purports to be a test of legal
cause that is universally applicable to all tort and criminal cases.
This test, too, is justified on policy grounds and does not pretend to
have anything to do with factual or scientific causation. Doctrinally,
however, the test differs from a simple foreseeability test.

Consider first the arena from which the test takes its name, which is
from crimes or torts of risk creation. If the defendant is
criminally charged with negligent homicide (or wrongful death in
torts), for example, this test requires that the death of the victim
be within the risk that made the actor’s action negligent. If it
was negligent to drop a can of nitroglycerin because it might explode
and kill the victim, but instead it kills him by cutting his toe and
causing him to bleed to death, then the harm that happened (bleeding)
was not within the risk of harm (explosion) that made it negligent to
drop the can (American Law Institute 1934). Similarly, if the charge
is manslaughter (for which consciousness of the risk is required in
some jurisdictions), this test requires that the death of the victim
be within the risk the awareness of which made the defendant’s
action reckless.

Extension of this test to non-risk-creation crimes or torts requires
some modification. For crimes or torts of strict liability, where no
mens rea is required, the test requires that the harm that
happened be one of the types of harms the risk of which motivated the
lawmaker to prohibit the behavior. For torts or crimes requiring
knowledge (or “general intention”) for their mens
rea, the test asks whether the harm that happened was an instance
of the type of harm the foresight of which by the defendant made her
culpable. For torts or crimes requiring purpose (or “specific
intent’) for their mens rea, the test asks whether the
harm that happened was an instance of the type of harm intended by the
defendant which intention made him culpable.

What motivates all of these variations of the harm-within-the-risk
test is the following insight: when assessing culpable mens
rea, there is always a “fit problem”. Suppose a defendant
intends to hit his victim in the face with a stick; suppose further he
intends the hit to put out the victim’s left eye. As it happens,
the victim turns suddenly as she is being hit, and loses her right ear
to the blow. Whether the harm that happened (right ear loss) is an
instance of the type of harm intended (left eye loss) is what is
called the fit problem. Fact finders have to fit the mental state the
defendant had to the actual result he achieved and ask whether it is
close enough for him to be punished for a crime of intent like mayhem.
(If it is not close enough, then he may yet be found guilty of some
lesser tort or crime of battery or reckless endangerment.)

The essential claim behind the harm-within-the-risk test is that
“legal cause” is the label lawyers should put on a problem
of culpability, the problem called the fit problem. Proponents of this
test urge that legal cause, properly understood, is really a mens
rea doctrine, not a doctrine of causation at all (American Law
Institute 1985).

The main problem for the harm-within-the-risk test does not lie in any
of the directions we have just explored with respect to foreseeability
as a test. The harm-within-the-risk test is in the service of a
justice-oriented policy in its seeking of a true desert-determiner
(culpable mental state), and it does not ask a redundant question. To
grade culpability by the mental states of intention, foresight, and
risk, we do have to match the harm done to the type of harm intended,
foreseen, or unreasonably risked. The real questions for the
harm-within-the-risk test are why this culpability question is
labelled as a problem of legal causation, and whether this
grading by culpable mental states is all that is or should be going on
under the rubric of “legal cause”.

Consider this last question in light of two well-known sorts of legal
cause cases. It is a time-honored maxim of criminal and tort law that
“you take your victim as you find him”. Standard
translation: no matter how abnormal may be the victim’s
susceptibilities to injury, and no matter how unforeseeable such
injuries may therefore be, a defendant is held to legally cause such
injuries. Hit the proverbial thin-skulled man, and you have legally
caused his death if he dies, no matter how rare his condition might
be. This is hard to square with the harm-within-the-risk test. A
defendant who intends to hit or to cut does not necessarily (or even
usually) intend to kill. A defendant who foresees that his acts will
cause the victim to be struck or cut, does not necessarily (or even
usually) foresee that the victim will die. A defendant who negligently
risks that his acts will cause a victim to be struck or cut is not
necessarily (or even usually) negligent because he risked death.

The second sort of case involves what are often called
“intervening” or “superseding” causes. Suppose
the defendant sets explosives next to a prison wall intending to blow
the wall and to get certain inmates out. He foresees to a practical
certainty that the explosion will kill the guard on the other side of
the wall. He lights the fuse to the bomb and leaves. As it happens,
the fuse goes out. However, a stranger passes by the wall, sees the
bomb, and relights the fuse for the pleasure of seeing an explosion;
or, alternatively, lightning hits the fuse, reigniting it and setting
off the bomb. When the guard on the other side of the wall is killed
by the blast, standard doctrines of intervening causation hold that
the defendant did not legally cause the death of the guard. Yet this
is hard to square with the result that seemingly should obtain under
the harm-within-the-risk test. After all, did not the defendant
foresee just the type of harm an instance of which did occur? Because
the harm-within-the-risk question asks a simple type-to-token
question—was the particular harm that happened an instance of
the type of harm whose foresight by the defendant made him
culpable—the test is blind to freakishness of causal route
(Moore 2009a: ch. 10).

The American Law Institute’s Model Penal Code modifies its
adoption of the harm-within-the-risk test in section 2.03 by denying
liability for a harm within the risk that is “too remote or
accidental in its occurrence to have a [just] bearing on the
actor’s liability or on the gravity of his offense”
(American Law Institute 1962). This language was not intended as a
general, stand-alone test of proximate causation, as it is sometimes
construed to be (Dan-Cohen 1983). Rather, the language gives a
qualifying caveat to the more general harm within the risk test of the
Model Penal Code. Such a caveat is an explicit recognition of the
inability of the harm-within-the-risk test to accommodate the issues
commonly adjudicated as intervening cause issues.

Such a recognition is not nearly broad enough to cover the inadequacy
of the harm-within-the-risk approach. The basic problem with the test
is that it ignores all the issues traditionally adjudicated
under the concept of legal cause. The test is blind not only to
freakishness of causal route in the intervening cause situations,
blind not only to the distinction between antecedent versus
after-arising abnormalities so crucial to resolution of the
thin-skulled man kind of issue, but the test also ignores all those
issues of remoteness sought to be captured by Sir Francis
Bacon’s coinage “proximate causation”. Even where
there is no sudden “break” in the chain of causation as in
the intervening cause cases, there is a strong sense that causation
peters out over space and time. Caesar’s crossing the Rubicon
may well be a necessary condition for your reading of this essay, but
so many other events have also contributed that Caesar’s causal
responsibility has long since petered out. The logical relationship at
the heart of the harm-within-the-risk test—“was the
particular harm that happened an instance of the type of harm whose
risk, foresight, or intention made the defendant
culpable?”—is incapable of capturing this sensitivity to
remoteness. As such, the harm-within-the-risk test is blind to the
basic issue adjudicated under “legal cause”. The
harm-within-the-risk test asks a question that well serves
justice-oriented theories of torts and criminal law, but it asks it in
the wrong place and in substitution of other questions needing an
answer for desert to be assessed.

We turn now from the policy-based tests of proximate causation to
those tests based on the view that proximate causation, like cause in
fact, has to do with real causal relations in the world. The oldest of
these tests is that suggested by Sir Francis Bacon’s coinage
“causa proxima” (1630: first maxim). The simple
idea behind such a remoteness test is that causation is a scalar
relation—a more-or-less sort of thing, not an all-or-nothing
sort of thing—and that it peters out over time.

A criticism of the remoteness test, often voiced in the legal
literature, is that distance in space and remoteness in time are
irrelevant to degrees of causal contribution. Examples like People
v. Botkin, where poisoned candy went a great distance (from
California to the victim in New Jersey), or an undetonated bomb left
buried for many years before it explodes and injures a victim, are
trotted out in support of the criticism. Justice Cardozo rejoined that
such criticism surely ran counter to strong community sentiment that
spatiotemporal distance does matter to degrees of causal contribution
(Bird v. St. Paul F. and Minneapolis Ins. Co.), but one would
hope that one could do better than that. Spatiotemporal distance is
perhaps a serviceable proxy for the number of events or states of
affairs through which a cause exerts its influence on its effects, and
the number of events could be relevant to the degree of causal
contribution. This is the metaphysical view that causation
“tires” through its links and that in this way the
relation is not fully a transitive one.

A second and quite distinct kind of cause-based proximate cause test
is the “direct cause” test. Despite the name, this test
does not require that there be a complete absence of any
event or state of affairs intervening between a cause and its effect,
for that cause to be “direct”. Not even the ancient
direct/indirect distinction between the writs of trespass and
trespass-on-the-case in torts was this stringent in its requirement of
directness (for trespass; Scott v. Shepard). On the contrary,
chains can be sufficiently direct for the direct cause test
even though they are quite long chains extending over considerable
space and time. It is only if a special kind of event—an
“intervening” (aka “superseding”,
“extraneous”) cause—intervenes that the chain is
insufficiently direct. The heart of the direct cause test is thus the
idea that there are these chain-breaking, intervening causes.

Beginning with a series of articles in the 1950s and culminating in
their massive book of 1959, Causation in the Law, second
edition 1985, Herbert Hart and Tony Honoré sought to describe
the idea of intervening causation that they saw the law adopting from
everyday causal idioms. One can see their concept most easily in three
steps. First, presuppose some version of the counterfactual analysis:
a cause is at least a necessary condition for its effect, or perhaps a
NESS condition (Honoré 1997). Second, a cause is not just
any necessary condition; rather, out of the plethora of
conditions necessary for the happening of any event, only two sorts
are eligible to be causes rather than mere “background
conditions:” free, informed, voluntary human actions, and those
abnormal conjunctions of natural events we colloquially refer to as
“coincidences”. Third, such voluntary human action and
abnormal natural events cause a given effect only if some other
voluntary human action or abnormal natural event does not intervene
between the first such event and its putative effect. Such salient
events, in other words, are breakers of causal chains
(“intervening causes”) as much as they are initiators of
causal chains, so if they do intervene they relegate all earlier such
events to the status of mere background conditions.

Hart and Honoré built on considerable case-law support for
their two candidates for intervening causes (Carpenter 1932,
1940–43; Eldredge 1937). Indeed, it is arguable that the basic
distinction between principal and accomplice liability in criminal law
depends in large part on this conceptualization of causation (Kadish
1985), as does the tort law distinction between “in
concert” and “concurrent causer” kinds of joint
tort-feasors. One worry for this view of causation, nonetheless, is
that it is incomplete with respect to the remoteness range of issues
usually dealt with under the rubric of “legal cause” in
the law. Causation in the law fades out gradually as much it breaks
off suddenly, and the direct cause analysis ignores this.

5.4 Unified (or “one tier”) approaches to causation in the law

The problems with the conventional legal analysis of
causation—in terms of a bifurcation into cause in fact and
proximate causation—have tempted some legal theorists to abandon
the bifurcation of causation in the law and to search for a unitary
notion of causation that is much more discriminating (in what it
allows as a cause) than the hopelessly promiscuous counterfactual
cause-in-fact test of the conventional analysis. Indeed, the search is
for a unitary concept of causation that is so discriminating that it
can do the work that on the conventional analysis is done by both
cause-in-fact and proximate cause doctrines. It is far from obvious
that causation is in fact a sufficiently discriminating relation that
it can do this much work in assigning responsibility. Nonetheless,
there are three such proposals in the legal literature, each having
some doctrinal support in the law.

One we have seen already in the fourth variation in the counterfactual
test for cause in fact. If one does not ask whether the
defendant’s act was necessary for the occurrence of the
harm—if one instead and more discriminatingly asks whether that
aspect of her act that made her negligent or otherwise
culpable caused the harm—then one has a causal test almost as
discriminating as the simple counterfactual test coupled with a
harm-within-the-risk version of the proximate cause test (Keeton 1963;
Wright 1985b). This is not surprising, because both tests rule
ineligible any aspects of the defendant’s act that does
not make her culpable. For the aspect-causation view, such
culpability-irrelevant aspects of the defendant’s action are not
(relevantly) the cause of the harm; for the harm-within-the-risk test,
such culpability-irrelevant aspects of the defendant’s action do
not fit the culpable mental states of the defendant. Whether one puts
it as causation (the aspect-cause view), or as culpability (the
harm-within-the-risk view), the discriminating power is roughly the
same.

A second unified view of causation in the law is the oldest of these
kinds of proposals. It conceives of causation as a metaphysical
primitive. Causation is not reducible to any other sort of thing or
things, so there is little by way of an analysis that one can
say about it and so very little that juries should be told about it
(Smith 1911). The one thing we can say is that the causal relation is
a scalar relation, which is to say, a matter of degree. One thing can
be more of a cause of a certain event than another thing.
Given the scalarity of causation, all the law need do is draw the line
for liability somewhere on the scale marking degrees of causal
contribution. On matters that vary on a smooth continuum, it is
notoriously arbitrary to pick a precise break-point; where is the line
between middle age and old age, red and pink, bald and not-bald, or
caused and not-caused? This approach thus picks an
appropriately vague line below which one’s causal
contribution to a given harm will be ignored for purposes of assessing
responsibility. Let the defendant be responsible and liable for some
harm only when the degree of his causal contribution to that harm has
reached some non de minimus, or “substantial”,
magnitude. This is the original “substantial factor” test,
as articulated by Jeremiah Smith in 1911. To the common objection that
the test tells us little, its defenders reply that that is a virtue,
not a vice, for there is little to be said about causation. Like
hard-core pornography, causation is something we can “know when
we see it” (Potter Stewart’s language about pornography in
Jacobellis v. Ohio), without need of general definitions and
tests (Borgo 1979).

The third and last of these unified notions of causation is
physicalist in its ambitions. Some theorists have thought that we can
say more about the nature of the causal relation than that it is
scalar and that a substantial amount of it is required for
responsibility. On this third view, the nature of causation is to be
found in the mechanistic concepts of physics: matter in motion,
energy, force (Beale 1895, 1920; Epstein 1973). This test is similar
to the substantial factor view in its conceiving the causal relation
to be scalar but differs in its reductionist ambitions: causation is
not a primitive but can be reduced to some kind of physical
process.

This view handles easily the overdetermination cases that are such a
problem for the conventional analysis. When two fires join, two
bullets strike simultaneously, two motorcycles scare the same horse,
each is a cause of the harm because each is doing its physical work.
When one non-mortal wound is inflicted together with a larger, mortal
wound and the victim dies of loss of blood, each is a cause of death
because each did some of the physical work (loss of blood) leading to
death (People v. Lewis).

Such a mechanistic conception of causation is mostly a suggestion in
the legal literature because of the elusive and seemingly mysterious
use of “energy” and “force” by legal theorists
(Hart & Honoré 1959). One suspects that some such view is
often applied by jurors, but unless theorists can spell out the
general nature of the relation being intuitively applied by jurors,
this test tends to collapse to the metaphysically sparer (because
primitivist) substantial factor test.

5.5 Summary of the differing concepts of causation in the law

As we have seen, the Anglo-American law of torts and of crimes has a
bafflingly large number of conceptions of legal causation. Displayed
below is a review of what has been described above, organized by the
variables discussed earlier.

Conventional bifurcated test: legal causation is constituted by
two distinct components, cause- in-fact and proximate causation, with
each component of this bifurcated test having contested meanings:

Cause-in-fact tests

Explicitly defined counterfactual test: the defendant’s
action must be necessary to the occurrence of the harm.

Modified counterfactual tests, where the defendant’s act
must be:

A necessary element of a set of factors that are together
sufficient for the harm, where the total set of factors is itself
unnecessary for that harm to have occurred (the “INUS” and
“NESS” tests)

Necessary to every detail in the time, place, and manner of an
effect’s occurrence

Necessary to accelerations (but not retardings) of the
effect

Not necessary in the sense that the existence of
the act is necessary, so long as that aspect of the
defendant’s action as made that act culpable, is necessary

A “substantial factor” in the production of the harm,
where the necessity of that act is an always sufficient criterion of a
causal factor being “substantial” while not being a
necessary criterion

Necessary to an increase in the chance of an effect
occurring (rather than being necessary to the effect actually
occurring)

Tests for causal skeptics: cause in fact as a conclusion of
policy rather than a natural relation existing antecedent to law

Ad hoc policy balancing in each case where the resulting
policy balance is honored as a conclusion of “proximate
causation” in that case

Rules justified by policy balancing, such as:

Year and a day rule

First house rule

Last wrongdoer rule

Tests based on the single policy of gauging culpability (mental
state) of the actor

Foreseeability test: was the harm foreseeable to the defendant as
he acted?

Harm-within-the-risk test: was the harm that occurred an instance
of the type of harm the risk of which (or the intent or foresight of
which by the defendant) made the defendant’s action negligent
(or otherwise culpable)?

Tests regarding proximate causation to be a matter of fact (about
real causal relations) rather than a matter of policy

Space-time proximity tests and the petering out of causation as
it runs through a large number of events in the chain between cause
and effect

Direct cause test: sudden breaks in the causal chain formed by
the existence of “intervening” or
“superseding” causes that literally break causal chains
that would otherwise exist

Tests regarding proximate causation to be partly causal and partly
policy: direct cause combined with the requirement that the
intervening cause be unforeseeable to the defendant at the time she
acted

6. Conclusion

Although it is possible to hold the view that causation in the law
shares nothing with causation in science and in everyday life (save
use of the same word), such a view is very counterintuitive; some
relation between the two concepts of causation surely exists. That
leaves two more plausible views of this relation. A strong view of
this relation would be that the concepts are the same. The three
unified tests for legal causation last considered, and the two
metaphysical views of proximate causation earlier mentioned, all would
make such a strong relation plausible. A weaker view of this relation
would be to regard part of the law’s concept of
causation—“cause-in-fact”—to be the same as
causation in science and everyday life, but to regard the other
part—“proximate causation”—to be the
conclusions of policy analyses having nothing to do with anything that
could be thought of as causation in any ordinary sense.

To decide which version of this relation is the correct one, one has
to adjudicate between the various competing conceptions of causation
in the law that we have examined. To have a baseline of comparison,
one must also resolve the many conundrums surrounding the search for
the true metaphysics of causation in philosophy; among other things,
this involves hiving off all the features of ordinary usage of
“cause” that are merely pragmatic features of appropriate
utterance rather than semantic features fixing the reference of the
term. These are daunting tasks to be done on both sides of the
equation. To complete them, truly the lawyer must “adventure
himself with philosophers in the logical and metaphysical controversies that beset the idea of cause”
(Pollack 1901: 36). For philosophical lawyers and legal philosophers,
that will not be a cost but a benefit.

Related Entries

Acknowledgments

The author would like to acknowledge the work of Antony Honoré
and John Gardner on the previous entry in the SEP on this entry. The
present entry pursues the same basic questions as did they in their
earlier entry, as outlined in the present opening paragraph.